code: def concatenate_csv(train_csv, vali_csv, test_csv, output_csv):
      concatenated_df = concatenate_files(
          train_csv, vali_csv, test_csv, read_csv, LOCAL_BACKEND
      )
  
      logger.info("Saving concatenated dataset as csv..")
      concatenated_df.to_csv(output_csv, encoding="utf-8", index=False)
      logger.info("done")
  
file_path: ludwig/ludwig/data/concatenate_datasets.py
imports: import argparse
  import logging
  import numpy
  from ludwig.backend import LOCAL_BACKEND
  from ludwig.constants import SPLIT
  from ludwig.utils.data_utils import read_csv
label_desc: Use image node_id 1 for calling a global function with example usage: concatenate_csv(train_csv, vali_csv, test_csv, output_csv) without return types